The invention concerns a device for dispensing a prescribed product, in particular agar, into Petri dishes.
Petri dishes are small dishes of circular contour, in transparent plastic material, which contain a nutrient product such as an agar medium; they are used as medium for the development of cultures containing micro-organisms and are used in large number by analysis laboratories, in particular for medical research and in industry. Each Petri dish has a removable lid able to be placed over a bottom part that is less wide than the lid.
For product dispensing, a mechanical device is provided to open the dish and to transfer the open bottom part towards a product dispensing station which has a dispensing head comprising a nozzle through which product is dispensed into the bottom part. One of the problems raised by this dispensing station is related to the non-liquid consistency of the product dispensed thereat. Most often this product is viscous, in particular if it is agar. Owing to the viscosity thereof the product tends not to be uniformly distributed inside the bottom part of the Petri dish. This problem is further aggravated if only a small amount of product is dispensed into the bottom part of the Petri dish.
It is therefore sought to obtain a dispensing device for uniform distribution of product in the bottom part of a Petri dish, irrespective of the quantity of dispensed product and without the risk of spilling product outside the bottom part of the Petri dish. For this purpose, a first subject of the invention is a device for dispensing a prescribed product into at least one Petri dish, each Petri dish comprising a removable lid able to be arranged over a bottom part that is less wide than the lid,
the device comprising means for bringing the Petri dish to a dispensing station, where the Petri dish is held with a space between its lid and its bottom part to allow the dispensing of the product via a product dispensing head comprising a nozzle outputting product towards the bottom part when the nozzle is in a dispensing position,
characterized in that the device further comprises a piston comprising a tray for supporting the bottom part at the product dispensing station, and means for driving the tray in rotation around itself relative to the dispensing head, arranged to rotate the bottom part relative to the dispensing head situated in the position for dispensing product into the bottom part, in which the product outlet nozzle is arranged relative to the tray to dispense product into the bottom part set in rotation.
According to embodiments of the invention:
The speed at which the tray rotates around itself is between 10 and 100 rotations per minute.
The means for driving in rotation are designed to cause the tray to rotate around itself about a geometric axis of rotation, the nozzle comprises a product outlet end located away from the geometric axis of rotation of the tray set in rotation around itself, when in dispensing position.
The means for driving in rotation are designed to cause the tray to rotate around itself about a geometric axis of rotation, the outlet nozzle is arranged to dispense product into a region of the bottom part, said region being located at a distance from the geometric axis of rotation of the tray set in rotation, when in the dispensing position.
The tray comprises an upper surface that is concave from its centre towards its periphery to receive the bottom part of the Petri dish.
Said upper surface of the tray comprises a peripheral contacting part for contact with the bottom part of the Petri dish.
The tray comprises a recess in its centre on its upper surface.
The upper surface of the tray comprises a first peripheral contacting portion for contact with the bottom part of the Petri dish, this first contacting portion is in a material having greater adherence than the material of a second portion of the upper surface of the tray, surrounded by this first peripheral contacting portion.
The first peripheral contacting portion is a rubber material, whilst the second portion surrounded by this first peripheral contacting portion is metallic.
The transfer means comprise a transfer member for transferring the bottom part as far as a stop position at the dispensing station, the transfer member having an upper opening for supporting the lid of the Petri dish above a second lower opening for supporting the bottom part of the Petri dish, said tray being capable of passing through the openings to lift the bottom part of the Petri dish into the lid, passing through their respective support openings, when the transfer member is in the stop position at the dispensing station.
A column for the vertical guiding of Petri dishes is arranged above the piston to receive a Petri dish whose bottom part has been lifted up into its lid via said piston at the filling station, the piston being arranged to move the Petri dish with its bottom part lifted up into its lid from the transfer member to said column for vertical guiding of the Petri dishes, said column for vertically guiding of the Petri dishes comprising means to retain the Petri dish whose bottom part has been lifted into its lid and which has been brought by the piston.
A further subject of the invention is a method for dispensing a prescribed product into at least one Petri dish by means of the dispensing device such as described above, each Petri dish comprising a removable lid able to be placed over a bottom part that is of smaller width, a method in which the Petri dish is opened to hold its lid away from its bottom part, the bottom part is brought to a dispensing station, the dispensing head is placed in a dispensing position to dispense product into the bottom part positioned at the dispensing station, characterized in that the bottom part of the Petri dish is positioned on a piston comprising a tray rotating around itself, to cause the bottom part to rotate around itself throughout the entire time the product is dispensed into the bottom part from the dispensing head in dispensing position at said station.